Electric actuators with variable motor speed offer an effective solution for automating large penstocks in settings such as sewage treatment plants, retention basins and flood-protection systems. A modernisation project at Thames Water's Beckton Sewage Treatment Works demonstrates the benefits: by swapping the existing actuators for high-performance AUMA SAV variable-speed actuators, the upgrade preserves the operability of 12 large penstocks at the plant's coarse screen outlets while cutting mechanical stress and supporting reliable, efficient process control.

Built in 1864 in the east London borough of Newham and spanning more than 100 hectares, Beckton STW ranks among Europe's largest sewage treatment works, serving much of London north of the River Thames.

Fig. 1 AUMA SAV actuators enable dependable, efficient penstock operation at Beckton STW, London (image source: AUMA)

The project demanded a "sympathetic" approach to the existing penstocks. AUMA advised replacing the old single-speed actuators with variable-speed units: the motor runs at the ideal speed throughout each opening or closing cycle, so heavy penstocks move gently with soft starts and stops, reducing shocks — while long strokes are traveled faster, cutting operating time.

Each new SAV actuator has an individual automatic greasing cartridge mounted on the thrust base — one per rising stem — with timed release settings that lubricate both the bearings and the penstock stem, extending the service life of the whole system.

Controls are standard parallel controls with 24 V DC commands and 4–20 mA position feedback; Profibus interfaces were also fitted — unused for now, but allowing future Profibus upgrades without any hardware or software changes.

All 12 penstocks were fully tested and commissioned at project completion. Site operatives now work more efficiently, and Beckton STW is prepared for future challenges.

Fig. 2 Thanks to adjustable motor speed, the SAV actuators lower mechanical stress on the twelve penstocks at the coarse screen outlets, extending their service lives (image source: AUMA)

Related reading: AUMA Electric Actuator Field Commissioning: Limit Setting, DUO Intermediate Switches, Torque & Feedback Calibration; AUMA SA/SAR Series: Wiring, Limit & Torque Setting and Feedback Calibration; see also the AUMA brand column.